Power supply lead inductance is part of the equation. We are dealing with an RLC circuit, which can be underdamped leading to ringing. Take a look at the attached files which may provide some insight.
Also, my working career was in the electric utility industry where I designed power factor correction capacitor installations on a routine basis, typically controlling up to 1200 kVAr banks on 12kV systems using vacuum switches. These are also RLC circuits which ring in the microsecond time frame and believe me I had to design to mitigate some monstrous surges. These transients can show up (usually significantly attenuated) at the customer service level and may explain some of the observed random failures of customer equipment. So our radios need well designed power supplies with immunity to things coming down the mains which isn't always lightning. So stay away from the cheap stuff, no matter where manufactured.
